Modern phased array radars typically use thousands of radiating elements. Behind the radiators are other microwave components such as amplifiers, phase shifters, and power divider networks. The current trend in module design is to integrate a number of these microwave functions together into a common enclosure. These integrated designs save considerable production costs since they reduce the total number of parts and also eliminate the expense of testing each of the parts separately.
In the past all the modules have been made identical, with equal amplitude outputs, since this is more economical than building many different module types. Future requirements on the modules call for amplitude taper across the module in order to reduce antenna sidelobe levels.
Various types of power dividers exist to split incident power both equally and unequally, for example, split-tee couplers ("Split-Tee Power Divider," L. I. Parad and R. L. Moynihan, IEEE Trans, MTT, January 1965, pp. 91-95); coupled line couplers ("Coupled Strip Transmission Line Filters and Directional Couplers," E. M. T. Jones and J. T. Bolljahn, IRE Trans. MTT, Vol. MTT-4, April 1956, pp. 75-81); lange couplers ("An Interdigitated Stripline Quadrature Hybrid," J. Lange, IEEE MTT, December 1969, pp. 1150-1151); hybrid ring couplers ("Hybrid Ring Directional Coupler for Arbitrary Power Divisions," C. Y. Pon, IRE Trans. MTT, November 1961, pp. 529--535); and Wilkenson couplers ("An N-Way Hybrid Power Divider," E. J. Wilkenson, IRE Trans. MTT, January 1960, pp. 116-117).